[Story]: PM Buddy — members and project roles

[LinseCed]

User Story

As a PM in the buddy's team mode, I want to add people to my project, remove them, and give them project roles — so I can staff the project from the conversation. Nothing changes until I confirm it.

Context & Motivation

• Type: Functional (agent actions on the PM surface)
• Parent epic: 05 EPIC - Agent Orchestration & Workflow Actions #54 (05 EPIC – Agent Orchestration & Workflow Actions)
• Teams: team:backend
• Concept: pm-buddy-concept.md
• Builds on: [Story]: PM Buddy — run a managed project from the buddy #312 (team mode, stored proposals, mounting by area)

The critical piece of this story: a manager has no way to find somebody who is not on the project yet — every admin project route is admin-only and there is no user lookup. The lookup this story adds is exact-match only (email or GitHub login, one result), so the buddy cannot be used to browse every account.

In Scope

• Exact-match user lookup for adding members
• Add and remove members
• Assign and unassign project roles on the managed project

Acceptance Criteria

• A manager can add a person found by exact email or GitHub login
• A manager can remove a member; removing the project's manager is refused
• A manager can assign and unassign project roles for members of their project only
• Role catalog, role skills and the skill catalog are not reachable from team mode
• Every change is a proposal until confirmed

Technical Notes

• Tool labels fall back to a generic label in the frontend, and the persona only describes mounted tools, so no frontend or AI work is needed.

Sub-Tasks (by team)

• Backend — team-mode actions for members and project roles (Team-mode actions: members and project roles sprintstart-backend#226)